Expandable threaded arcuate interbody spinal fusion implant with cylindrical configuration during insertion

ABSTRACT

An at least in part cylindrical threaded interbody spinal fusion implant having an expandable height.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to an improved interbody(for placement at least in part between adjacent vertebral bodies)threaded spinal fusion implant only for the immobilization of vertebraeand not to non-threaded implants. In particular, the invention relatesto a threaded spinal fusion implant that is selectively directionallyexpandable and which specifically has height raising capabilities thatare utilized once the implant is initially positioned. Moreparticularly, the invention relates to a threaded implant having arcuateportions of upper and lower members that in a first, collapsed, orinsertion position are parallel to one another and form at least aportion of a cylinder along a substantial portion of the length of theimplant.

[0003] 2. Description of the Related Art

[0004] Threaded spinal fusion implants are known in the related art. Thefirst artificial threaded spinal fusion implant was invented byMichelson and is disclosed in U.S. Pat. No. 5,015,247, which is herebyincorporated by reference.

[0005] Lordotic, frusto-conical, or tapered, threaded spinal fusionimplants are also known in the art. By way of example, Michelson hasinvented such implants as disclosed in U.S. application Ser. No.08/480,904, which is hereby incorporated by reference.

[0006] Expandable fusion implants are known in the related art. Thefirst expandable spinal fusion (allowing for the growth of bone fromvertebral body to vertebral body through the implant) implant wasinvented by Michelson and is disclosed in U.S. Pat. No. 5,776,199, whichis hereby incorporated by reference.

[0007] Lordotic, frusto-conical, or tapered, spinal fusion implants havethe advantage of restoring or enhancing spinal lordosis. Threaded spinalfusion implants offer the advantage of being easily positioned in theimplantation space and of having excellent fastening or holdingfeatures. Expandable fusion implants offer the advantage of allowing forthe placement of a potentially larger implant through a smaller openingin a patient's body. Selective expansion along a single direction, (e.g.vertically only when correctly installed) offers the advantage ofincreasing the height of the implant and therefore the distraction ofthe disc space, but without a concomitant increase in the width of theimplant.

[0008] There exists a need for an artificial interbody spinal fusionimplant providing for all of the aforementioned advantages incombination.

SUMMARY OF THE INVENTION

[0009] In accordance with the present invention, as embodied and broadlydescribed herein, there is provided an expandable threaded artificialinterbody spinal fusion implant, generally cylindrical when inserted,for insertion across a disc space between two adjacent vertebral bodiesof a human spine. The threaded implant of the present invention includesan upper member having an arcuate portion adapted for placement towardand at least in part within one of the adjacent vertebral bodies and alower member having an arcuate portion adapted for placement toward andat least in part within the other of the adjacent vertebral bodies. Thearcuate portions of the upper and lower members have at least oneopening in communication with one another for permitting for the growthof bone from a vertebral body to an adjacent vertebral body through theimplant. The upper and lower members are articulated therebetween,preferably proximate one of the proximal ends and the distal ends of theupper and lower members and preferably allow for divergence between thearticulating members at the end opposite the articulating end of theimplant. The upper and lower members have a first position relative toone another that allows for a collapsed implant height and a secondposition relative to one another that allows for an increased height.The arcuate portions of the upper and lower members in the firstposition of the present invention are parallel to one another and format least a portion of a cylinder along the length of the implant. Aportion of at least one helical thread is on the exterior of each of theopposed arcuate portions of the upper and lower members for engaging theadjacent vertebral bodies. The upper and lower members have a leading ordistal end, an opposite trailing or proximal end, and a lengththerebetween. A blocker that is preferably in the form of an expander islocated proximate at least one of the ends for holding at least aportion of the upper and lower members apart so as to maintain theincreased height of the implant and resist the collapse of the implantto the collapsed implant height. Expansion of the implant preferablyincreases the implant height only, that is in a plane passing throughthe mid-longitudinal axis of the implant and the upper and lowermembers.

[0010] The blocker need not be in contact with the upper and lowermembers when the implant is initially inserted into the implantationspace. The blocker may be a block or any type of spacer that is insertedbetween or otherwise holds apart the articulated upper and lower membersafter the implant is positioned so as to hold portions of the upper andlower members spaced apart the optimal height and angulation relative toone another. That is the implant may be expanded with an extrinsic tooland then the expanded portions held apart in the second position by athird body blocker or blockers placed therebetween. Further, a physicianmay be able to select from a series of blockers having different heightsusable with the same implant. The present invention includes expandingthe implant with a tool, such as a spreader or a distractor, but is notlimited to a scissors type, a rack and gear type, a threaded member typeor any other type of particular external expander tool mechanism. Eachtool nevertheless preferably engages the upper and the lower implantmembers to urge the implant apart. Then the blocker may be inserted intocontact with the upper and lower members to maintain the implant at anexpanded height. The height of the gap created by expanding the implantmay be measured so that the appropriately sized blocker or expander maybe inserted into contact with the upper and lower members depending uponthe amount of distraction of the implant desired by the physician.

[0011] In a preferred embodiment, the blocker is in contact with theupper and lower members prior to the implant expansion, and the blockeris itself the expander, which may be operated by an extrinsic tool. Byway of example only, the expander may rotate: to increase the height ofthe implant; in a single direction; more than 40 degrees and less than140 degrees and more preferably approximately 90 degrees to move from afirst insertion position to a second/deployed position; and in a planeperpendicular to the longitudinal axis of the implant to increase theheight of the implant. The expander preferably remains in the sameperpendicular plane relative to the longitudinal axis of the implantwhen rotated. In another embodiment the expander may be a member, suchas a plate, a rod, or of any other configuration suitable for theintended purpose initially within the interior between the upper andlower members in a collapsed position that is erected to a more erectposition when the implant is in the expanded position. The expander canitself be hollow or solid.

[0012] In a preferred embodiment, the expander preferably has meansincluding, but not limited to, an opening, a projection, or a detentadapted to cooperatively engage a tool used to rotate the expander toincrease the height of the implant. The opening, projection, or detentis adapted to cooperatively engage a tool that preferably rotates aboutan axis parallel to the longitudinal axis the implant to rotate theexpander to increase the height of the implant. Rather then having anopening, a projection, a detent, or a central aperture, the expander mayhave two or more recesses or holes placed on or through the proximalface to engage a tool. In an alternative embodiment of the expander,cutouts may be positioned along a portion of the perimeter of theexpander.

[0013] The expander is preferably located proximate at least one of theproximal end or the distal end of the upper and lower members. Theexpander, however, need not be so located. The expander may be spacedaway from the end and even permit a hollow portion to exist on both theproximate and distal sides of the expander. The upper and lower memberspreferably have an interior surface therebetween and a hollow definedtherein with the expander located proximate one of the longitudinal endsof that interior hollow. The hollow between the ends of the upper andlower members is preferably unobstructed by the expander so as to permitgrowth of bone directly through the hollow unobstructed by the expanderfrom vertebral body to vertebral body through the implant transverse tothe longitudinal axis. The implant may comprise a second and lesserhollow extending at least in part from said expander to the end of theupper and lower members proximate that expander. A preferred expandermechanism includes an expander in combination with cooperating surfacesof the end wall of the implant that guide and support the expander.

[0014] Preferred forms of interbody spinal fusion implants have asubstantial hollow portion. Certain expandable interbody spinal fusionimplants that increase in height only of the related art contain anexpansion mechanism passing longitudinally therethrough or an expansionmechanism that is configured for movement of the expansion mechanismfrom proximate one end of the hollow portion to proximate the other endof the hollow portion, thus requiring the expander to pass through thelength of the hollow portion. A preferred embodiment of the presentinvention overcomes these limitations.

[0015] The expander moves the arcuate portions of the upper and lowermembers from a parallel orientation to an angled orientation relative toone another or from a first height at each end to a second and greaterheight at at least one and possibly both ends, but in either event thearcuate portions of the upper and lower members in the first orinsertion position are parallel to one another over a substantialportion of the length of the implant, and/or form at least a portion ofa cylinder along the length of the implant. Each of the upper and lowermembers may structurally cooperate with a blocker, or expander so as tokeep it located so as to function for its intended purpose. By way ofexample, each of the upper and lower members preferably has a trackwithin which the blocker may be captured or the expander rotated. Thetracks may be configured to permit the expander to rotate therein andthen to move from side to side therewithin. The track of the uppermember and the track of the lower member are preferably in the sameplane and the plane is preferably perpendicular to the longitudinal axisof the implant.

[0016] A preferred expander has a first height in a first or insertionposition and a greater second height when rotated or positioned into asecond or deployed position to increase the maximum height of theimplant from a first maximum height to a second maximum height. By wayof example, at least one of the tracks of the upper and lower memberspreferably has a cooperating surface and the expander has acorresponding cooperating surface that contacts the cooperating surfaceof the track to orient the expander in a predetermined position. Thecooperating surfaces preferably orient the expander within the implantsuch that the axis of rotation of the expander is parallel with thelongitudinal axis of the implant and, more preferably, center theexpander within the implant such that the axis of rotation of theexpander coincides with the longitudinal axis of the implant. As may beadvantageous for the further loading of the implant withfusion-promoting material, the expander may cooperate with the trackingsurfaces of the upper and lower members to allow the expander to slidefrom side-to-side for easier access to the implant interior.

[0017] The implant is preferably packed full of bone or otherfusion-promoting substances prior to expansion of the implant. Expansionof the implant results in a space being formed in the implant interiorinto which additional fusion promoting substances such as bone maypreferably be packed. Rotating the expander within the implant causes avoid that can be filled with bone. If the expander is configured topermit side-to-side movement, then packing of additional bone into theimplant is easy.

[0018] When installing a preferred implant from the posterior approachto the spine, the implant is driven from the trailing end and theexpander is at the leading end at the anterior aspect of the spine. Whenexpanded, the implant installed from the posterior aspect leaves a voidat the leading end of the implant near the anterior aspect of the spinebecause the leading end of the implant has been made taller.Additionally, the path left behind in the bone filled interior of theimplant by the tool used to access the expander through the bone filledinterior to position the expander is preferably packed with bone aswell.

[0019] In a preferred embodiment of the present invention, the expanderheight change from the first position to the second position correspondsto substantially the same change in height of the implant along at leasta portion of the length of the implant. The expander may be configuredin different ways. A preferred configuration for a rotational expanderincludes: a first dimension corresponding to the width of the expanderwhen the implant is initially inserted into the spine and to the heightof the rotational expander when the rotational expander is rotated toincrease the height of the implant; and a second dimension correspondingto the height of the expander when the implant is initially insertedinto the spine and to the width of the expander when the expander isrotated to increase the height of the implant. The first dimensionpreferably is greater than the second dimension.

[0020] The expander may have an upper surface, a lower surface, and sidesurfaces as defined when the expander is positioned after rotation toincrease the height of the implant. As used herein, the term “sidesurfaces” refers to those portions of the expander that extend from theupper member to the lower member after the expander has been rotatedinto its second or deployed position to increase the height of theimplant. The “upper” and “lower” expander surfaces refer to thoseportions of the expander that are in contact with the upper and lowermembers when the implant is in its second or expanded configuration.Each of the upper and lower surfaces of the expander may lie generallyin a plane and may be generally parallel to one another. The sidesurfaces and the upper and lower surfaces may be oriented so as tosubstantially form a parallelogram, which will typically be in the shapeof a rectangle generally.

[0021] A preferred expander is in the form of a modified rectangle orrhomboid. The expander generally has a longer dimension and a shorterdimension. When the expander is in a first position, the short dimensionspans the distance between the upper and lower members and when theexpander is in the second position, the expander's long dimension spansthe distance between the upper and lower members.

[0022] The expander may have a cross-section with the side surfacesintersecting the upper and the lower surfaces at junctions, which may betwo diametrically opposed corners and two diametrically opposed arcs.The two diametrically opposed arcs may be each of the same radius and,preferably, the diagonal or modified hypotenuse “MH” between the opposedarcs has a maximum dimension that generally approximates the distancebetween the upper and lower surfaces such that, when the expander isrotated from a first insertion position toward a second/deployedposition, no substantial over-distraction occurs between the adjacentvertebral bodies as would occur if the height of the implant wasincreased markedly beyond that obtained in the second/deployed position.The two diametrically opposed corners may form a 90-degree angle. Theexpander preferably has a fixed shape during movement from a firstinsertion position to a second/deployed position within the implant.

[0023] In a preferred embodiment, a modified hypotenuse or diagonal “MH”is the dimension between the two diametrically opposed arcs that allowsfor the rotation of the expander from a first position to a secondposition without substantial over-distraction occurring during thisprocess. The phrase “without substantial over-distraction” is defined asdistracting the vertebral bodies in the range of elastic deformation andshort of plastic deformation and tissue failure. To avoid any ambiguityregarding the phrase “without over-distraction,” this phrase and theindividual words contained therein are not being used as they may be intheir normal or ordinary use, but are being used as defined in thisapplication only. In the example of this rotational expander, the MHcould be identical in length to the height thereby assuring literally nooverdistraction. It may be preferred, however, to have the MH justslightly greater in length than the height to insure the stability ofthe expander in the expanded or second position because this would thenrequire additional force over the stable position to derotate theexpander.

[0024] In accordance with an embodiment of the present invention, asecond expander may be located between the upper and lower members formoving at least a portion of the upper and lower members away from oneanother to increase the height of the implant as defined by the maximumdistance between the arcuate portions of the upper and lower membersproximate that expander. All of the features described herein for theexpander may also be applicable to the second expander. Additionally,the second expander may be located proximate an end of the implantopposite the other expander, thereby providing an implant capable ofbeing expanded at both ends of the implant. The increased height of theimplant resulting from moving the two expanders may be constant orvaried along the length of the implant according to the desiredconfiguration of the implant and the relative dimensions of theindividual expanders. A given implant may be adapted to receive orcooperatively engage a series of progressively sized (taller) blockersor expanders to allow the surgeon to make a final height selection atthe time of surgery.

[0025] In accordance with an embodiment of the present invention, theimplant may include an expansion mechanism including the expander and atleast one partial wall structure preferably located proximate an implantend that guides and holds the expander in a predetermined position.

[0026] The implant may have an overlapping step-cut wall junctionbetween the upper and lower members, which offers as some of itsadvantages: increasing the lateral rigidity of the implant, holding theimplant in the closed first position until expanded, and to the extentdesired retaining the fusion-promoting materials within the implant. Thewall junction may be either solid or perforated.

[0027] One of the upper and lower members preferably has an interiorwall extending toward the other of the upper and lower members and, morepreferably, has two interior walls extending from each side of thearcuate portion. The interior walls may be aligned parallel with thelongitudinal axis of the implant. The other one of the upper and lowermembers preferably has an interior-contacting surface adapted to contactor receive the interior longitudinal wall.

[0028] By way of example, one of the upper and lower members may have alongitudinally extending interior wall, which is preferably unexposed,extending toward the other of the upper and lower members when theimplant is in an initial insertion position. When the implant is in thefinal expanded or deployed position the implant has a preferred shapesuch that each of the arcuate portions of the upper and lower membersare separated by at least a portion of interior wall, which in thisposition preferably has an exposed side.

[0029] The upper and lower members in certain embodiments arearticulated to one another so one of the respective ends of the upperand lower members remain articulated while the other of the respectiveends of the upper and lower members are free to move away from oneanother. In a preferred embodiment, the articulating means is achievedwithout a third member, such as an axle shaft, for example, passingthrough the implant. The articulating means preferably is formed intothe implant walls themselves, and in a further preference in such a waythat the two-implant halves may be articulated when at 90 degrees toeach other. The halves then are moved, much like a book closing, towardeach other prior to insertion into the implantation space in the spine.Once the upper and lower members are closed from the approximately 90degrees articulating position, much like closing the leaves of a book,the upper and lower members of the implant are locked together at thearticulation so that the members will not disarticulate when in use.Other types of articulation as would be known to one of ordinary skillin the art are within the scope of the present invention.

[0030] By way of example, the upper and lower members preferably have acooperating rotational articulation or pivot point between a proximateone of the proximal end and the distal end of the upper and lowermembers. The cooperating rotational articulation preferably is proximateone of the proximal end and the distal end of the upper and lowermembers at an end opposite the expander when only one end is to beexpanded. A preferred rotational articulation configuration includescooperating brackets and projections configured such that articulationtherebetween occurs when the upper and lower members are substantiallyperpendicular to one another. Such a configuration offers the advantagethat the brackets and the projections will not disengage one anotherwhen articulated for use such as insertion into the spine and subsequentexpansion within a range of movement of the upper and lower membersresulting from the expander positioning.

[0031] When the implant is in the final or expanded position the implantmay take the general form of a cylinder split along a horizontal planethrough its mid-longitudinal axis wedged upper half from lower half byan inclined plane.

[0032] At least one and preferably both of the upper and lower membersmay have a screw hole passing through the trailing end, which preferablyis adapted to receive a screw passing through the end of the upper andlower members and from the interior of the implant into each of theadjacent vertebral bodies to anchor the implant, further stabilize thosevertebral bodies relative to each other, prevent undesirable motion atthe vertebral body implant interfaces, increase the compressive load atthe implant trailing end, prevent rocking and thereby to mitigateagainst excessive peak loads, and to more uniformly distribute loadsimparted to the implant over the length of the implant to the adjacentvertebral bodies. The implant may have a side configured, when in theexpanded position, to cooperate with another interbody spinal fusionimplant so as to allow the pair of implants to have a reduced combinedwidth.

[0033] The trailing end of the implant preferably has a tool-engagingportion, but the implant may be adapted to cooperatively engage a driverat another location or by any means as would be known to one of ordinaryskill in the art. This tool-engaging portion is adapted to engage aninsertion tool that holds and rotates the implant into position. Theconfiguration of the tool-engaging portion may be an opening, and moreparticularly an opening that is along the longitudinal axis of theimplant to facilitate the use of an insertion tool that rotates theimplant into an inserted position. It is appreciated that thetool-engaging portion need not be an opening. A hole or a blind hole,threaded or otherwise, is preferred in another embodiment. In anotherpreferred embodiment the opening preferably is a threaded slot thatfunctions to cooperatively engage and disengage a tool for use ininserting the implant. In specific embodiments, the leading or trailingend may have wall portions, and/or be adapted to cooperatively engage acap. Either the end wall portions or a cap may have an opening oropenings which may function to hold fusion-promoting materials withinthe implant and/or, permit vascular access and bone growth therethrough.

[0034] For an embodiment of an implant of the present invention havingone expander, the main access opening is preferably at the end oppositefrom the expander. The main opening may be at either the distal orproximal end of the implant. The end of the upper and lower memberscontaining the expander may serve as a secondary access opening.

[0035] By way of example, an implant configured for insertion from ananterior approach may be initially packed from the distal or leading endof the implant. The implant is then driven into position. Once theexpander is moved into final position and any associated tool forpositioning the expander is withdrawn from the expander, any void in thebone packed into the implant interior may be filled. The expander may bemoved from side-to-side to pack more bone into the implant. In essence,the side-to-side movement of the expander provides for a secondaryaccess opening for accessing the hollow interior of the implant and forcompressively loading it with fusion-promoting substances. Theaccompanying drawings, which are incorporated in and constitute a partof this specification, are by way of example only and not limitation,and illustrate several embodiments of the invention, which together withthe description, serve to explain the principles of the invention. Thescope of the invention is limited only by the scope of the claims asfrom the present teachings other embodiments of the present inventionshall be apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 is an exploded perspective view of a spinal fusion implantof one embodiment of the present invention;

[0037]FIG. 1A is a perspective view of an alternative embodiment of ablocker in the form of an expander for use with the spinal fusionimplant of FIG. 1;

[0038]FIG. 1B is a perspective view of another alternative embodiment ofa blocker for use with the spinal fusion implant of FIG. 1;

[0039]FIG. 1C is a perspective view of yet another alternativeembodiment of a blocker for use with the spinal fusion implant of FIG.1;

[0040]FIG. 2 is a top plan view of the implant of FIG. 1;

[0041]FIG. 3 is a trailing end view of the implant of FIG. 1;

[0042]FIG. 4 is a side elevation view of the implant of FIG. 1;

[0043]FIG. 5 is a leading end view of the implant with the end cap thereattached of FIG. 1;

[0044]FIG. 6 is a cross-sectional view along line 6-6 of FIG. 2;

[0045]FIG. 7 is a cross-sectional view along line 7-7 of FIG. 5;

[0046]FIG. 8 is a side elevation view of an end cap for use with theimplant of FIG. 1;

[0047]FIG. 9 is a schematic representation of a geometric configurationof a cross-section of an expander in accordance with one embodiment ofthe present invention;

[0048]FIG. 10 is a trailing end perspective view of the implant of FIG.1;

[0049]FIG. 11 is a side view of the implant of FIG. 10 being insertedfrom a generally anterior approach to the spine into an implantationsite formed across a disc space and two adjacent vertebral bodies of thespine shown in partial cross-section;

[0050]FIG. 12A is a cross-sectional view of the implant of FIG. 1inserted in an implantation site formed across the disc space and twoadjacent vertebral bodies of the spine;

[0051]FIG. 12B is a cross-sectional view of the implant of FIG. 1inserted in an implantation site of FIG. 12A and expanded to place theadjacent vertebral bodies in proper lordosis;

[0052]FIG. 12C is a trailing end perspective view of the implant of FIG.1 with the implant in an expanded position;

[0053]FIG. 13 is a trailing end view of the anterior aspect of twoadjacent vertebral bodies and two implants of FIG. 1 implantedtherebetween in a final position;

[0054]FIG. 14 is a cross-sectional side view of an implantation siteformed posteriorly across the disc space between two adjacent vertebralbodies and a second embodiment of an implant of the present inventionfor posterior insertion being installed into the implantation site;

[0055]FIG. 15 is a cross-sectional side view of the implantation siteformed across the space between two adjacent vertebral bodies and theimplant of FIG. 14 installed into the implantation space;

[0056]FIG. 16 is a leading end perspective view of the implant of FIG.14;

[0057]FIG. 17 is a top plan view of another embodiment of the presentinvention inserted upon the lower vertebral body of an implantation siteformed anteriorly across a disc space with the vertebral body shown inpartial cross-section;

[0058]FIG. 18A is a cross-sectional side view of the implantation siteformed across the space between two adjacent vertebral bodies and one ofthe implants of FIG. 17 installed into the implantation space;

[0059]FIG. 18B is a trailing end view of the anterior aspect of twoadjacent vertebral bodies and the implant of FIG. 17 implantedtherebetween in an expanded position as well as another embodimentdesigned to be used as a side-by-side pair;

[0060]FIG. 19 is a cross-sectional side view of the implant of FIG. 18Awithout bone or other fusion-promoting substances shown therein for thepurpose of illustrating a preferred configuration for articulating theupper and lower members together with a hook and peg configuration thatprevents the implant from over expanding and with an alternative secondhook and peg shown on the right hand side of the figure in dashed lines;

[0061]FIG. 20 is a partial cross sectional view of an embodiment of aninterlocking wall design along line 21-21 of FIG. 19;

[0062]FIG. 21 is a partial cross sectional view of another embodiment ofan interlocking wall design along line 21-21 of FIG. 19;

[0063]FIG. 22A is a cross-sectional side view of an alternativeembodiment of an implant of the present invention with a pivotingtrailing end that is also a blocker in the trailing end openingposition;

[0064]FIG. 22B is a cross-sectional side view of an alternativeembodiment of an implant of the present invention with a pivotingtrailing end that is also a blocker with the trailing end in the closedposition; and

[0065]FIG. 23 is a trailing end perspective view of the implant of FIG.22B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] The following description is intended to be representative onlyand not limiting and many variations can be anticipated according tothese teachings, which are included within the scope of this inventiveteaching. Reference will now be made in detail to the preferredembodiments of this invention, examples of which are illustrated in theaccompanying drawings.

[0067] Shown in FIGS. 1-7 and 10-13, in accordance with the presentinvention, as embodied and broadly described herein, is one embodimentof an expandable threaded artificial interbody spinal fusion implant 100for anterior insertion across a disc space D between two adjacentvertebral bodies V of a human spine. Threaded implant 100 of the presentinvention includes an upper member 102 having an arcuate portion 104adapted for placement toward and at least in part within the upper ofthe adjacent vertebral bodies V and a lower member 106 having an arcuateportion 108 adapted for placement toward and at least in part within thelower of the adjacent vertebral bodies V. Arcuate portions 104, 108 ofupper and lower members 102, 106 have at least one opening 110, 112 incommunication with one another for permitting for the growth of bonefrom vertebral body V to adjacent vertebral body V through implant 100.Upper and lower members 102, 106 are articulated therebetween at anadjacent one of the proximal ends and the distal ends of upper and lowermembers 102, 106 and allow for rotation between the articulating membersat the end opposite the articulating end of implant 100. Upper and lowermembers 102, 106 have a first position relative to one another thatallows for a collapsed implant height and a second position relative toone another that allows for an increased height. Arcuate portions 104,108 of upper and lower members 102, 106 in the first position of thepresent invention are parallel to one another and form at least aportion of a cylinder along the length of implant 100. A portion 114,116 of at least one thread 118 is on an exterior 120 of each of opposedarcuate portions 104, 108 of upper and lower members 102, 106 forengaging adjacent vertebral bodies V.

[0068] While a specialized form of a blocker 121 is described insignificant detail below with reference to expander 122, blocker 121need not be in contact with upper and lower members 102, 106 whenimplant 100 is initially inserted into the implantation space. Blocker121 may be a block or any type of spacer that is inserted between thearticulated upper and lower members 102, 106 after implant 100 ispositioned so as to hold portions of the upper and lower members 102,106 spaced apart the optimal height and angulation relative to oneanother. That is the implant may be expanded with an extrinsic tool andthen the expanded portions held apart in the second position by a thirdbody blocker placed therebetween. Further, a physician may be able toselect from a series of blockers having different heights usable withthe same implant. The present invention includes expanding the implantwith a tool, such as a spreader or a distractor but is not limited to ascissors type, a rack and gear type, a threaded member type or any otherspecific type of movement mechanism. Each tool nevertheless preferablyengages upper and lower implant members 102, 106 to urge them apart.Blocker 121 is then inserted into contact with upper and lower members102, 106 to maintain implant 100 at an expanded height. The height ofthe gap created by expanding implant 100 may be measured so that theappropriately sized blocker 121 or specialized blocker, expander 122,may be inserted in implant 100 depending upon the amount of distractionof implant 100 desired by the surgeon.

[0069] Blocker 121 that is preferably in the form of expander 122 islocated proximate at least one of the ends of the implant upper andlower members 102, 106 and holds at least a portion of upper and lowermembers 102, 106 apart so as to maintain the increased height of implant100 and resist the collapse of implant 100 to the collapsed implantheight. Expander 122 in the present embodiment increases the implantheight as measured in a plane passing through the mid-longitudinal axisof implant 100 and upper and lower members 102, 106 during positioningof expander 122 and as may be desirable is capable of selectivelyincreasing the height of the implant only.

[0070] Expander 122 in the present embodiment is adapted to rotate in asingle direction approximately 90 degrees to move from an initial(first) insertion position 1, as best shown in FIGS. 1, 3 and 10, to afinal (second) deployed or expanded position F, as best shown in FIG.13, to increase the maximum height H of implant 100. Expander 122preferably rotates in a plane perpendicular to the longitudinal axis Lof implant 100 to increase the maximum height H of implant 100. Duringrotation, expander 122 remains in the same perpendicular plane relativeto the longitudinal axis L of the implant. It is appreciated that anexpander within the scope of the present invention may be designed to:rotate in either direction or both directions; rotate more than 40degrees and less than 140 degrees; rotate more or less than 90 degrees;or rotate in a plane other than perpendicular.

[0071] Expander 122 has an opening 124 adapted to cooperatively engage atool (not shown) used to rotate expander 122 to increase height H ofimplant 100. Opening 124 is adapted to cooperatively engage a tool thatpreferably rotates about an axis parallel to the longitudinal axis L ofimplant 100 to rotate expander 122 to increase height H of implant 100.Opening 124 also may be used as a passageway to pass fusion-promotingsubstances through expander 122 and into implant 100. It is appreciatedthat the expander may also include a projection, a detent, or any otherconfiguration in place of or in addition to an opening so as tocooperatively engage a tool to move the expander.

[0072] In an alternative embodiment, expander 122 could have cutoutsalong any portion of its perimeter not involved in the actual rotationas shown in FIG. 1A. In another alternative embodiment, a blocker 121having cutouts along a portion of its perimeter can be positioned intothe implant as shown in FIG. 1B. The cutouts can be used to engage araised area within the implant to lock blocker 121 or expander 122 intoposition or be used by the surgeon to grasp blocker 121 with a tool thatcooperatively engages the cutouts to facilitate inserting blocker 121into the implant. Rather then having an opening, a projection, a detent,or a central aperture, blocker 121 alternatively could have two or morerecesses or holes placed on or through the proximal face to engage atool as shown in FIG. 1C.

[0073] As shown in FIGS. 1, 6, 7, 10, 12A-12C, and 13, in one preferredembodiment of the present invention for anterior insertion, expander 122is located proximate the trailing end 126 of upper and lower members102, 106. While in a second embodiment as shown in FIGS. 14-16 forposterior insertion expander 222 is located proximate the leading end250. As shown if FIGS. 17-19, in third and fourth embodiments of thepresent invention for anterior insertion and possible use together,expanders 322 are located proximate each of leading and trailing ends330, 326 of implants 300.

[0074] Implant 100 preferably has an interior surface 128 and a hollow130 defined therein. Expander 122 of the present embodiment is locatedproximate interior surface 128 and more particularly proximate interiorsurface 128 at trailing end 126 of upper and lower members 102, 106. Asis preferred, hollow 130 between the ends is unobstructed by expander122 so as to allow for the unimpeded loading of the interior of theimplant with the desired fusion-promoting substances; thus, loading theimplant is easy. Further, this preferred configuration of implant 100makes available all of the volume of the hollow to containfusion-promoting substances and so as to permit for the growth of bonedirectly through the hollow unobstructed by the expander to adjacentvertebral bodies V. Unobstructed hollow 130 further allows for packingimplant 100 with fusion-promoting substances. It is appreciated thatdepending on the intended results, the expander also may be located atdistal end 126 or leading end 150 of upper and lower members 102, 106 oranywhere else within the implant. The unobstructed hollow preferably hasno mechanism extending along the longitudinal axis of the implant whenfinally deployed and the mechanism that moves the implant from a firstposition to a second position preferably does not move expander 122longitudinally through the hollow portion. The expander may work bypivoting on a surface in contact with an interior wall portion of atleast one of the upper and lower members 102, 106. Moreover, multipleexpanders may be used in contact with upper and lower members 102, 106at any location within the implant.

[0075] An alternative embodiment of an expander used with the presentinvention includes an expander having an external thread thatcooperatives with converging threaded portions of the upper and lowermembers 102, 106 to expand the implant as the expander is rotated intoposition. Another alternative embodiment of an expander includes anexpander having a cam configuration to expand the implant upon rotation.

[0076] The mechanism or tool used to move the expander is not part ofthe implant itself as the mechanism or tool is removed from the implantupon moving the expander, e.g. such as to rotate it into place and thusexpand the implant to the final expanded position.

[0077] Expander 122 of the present embodiment moves arcuate portions104, 108 of upper and lower members 102, 106 from a parallel orientationP, as shown in FIGS. 1 and 11 where implant 100 has a generally circularcross section in a first position at trailing end 126, to an angledorientation A, as shown in FIG. 12B where implant 100 has a generallyoblong cross section at trailing end 126, in a second position. Theimplant need not be a true cylinder as a cross section need not form acomplete circle having portions of the perimeter absent, less round,flattered, or other. It is appreciated that the expander also may movethe arcuate portions of the upper and lower members from a first heightat each end to a second and greater height at each end.

[0078] In this embodiment, each of upper and lower members 102, 106structurally cooperate with expander 122 so as to keep it located so asto function for its intended purpose. Each of upper and lower members102, 106 of the implant of FIG. 1 has a track 132, 134 within whichexpander 122 rotates. As best shown in FIGS. 1 and 13, track 132, 134 isconfigured to permit expander 122 to rotate therein and then to movefrom side to side within track 132, 134. Track 132 of upper member 102and track 134 of lower member 106 are in the same plane and the plane isperpendicular to the longitudinal axis of implant 100. It is appreciatedthat the track of the upper and lower members may be in differentplanes. Such a track design may be used with an expander with a step init or with offset tabs to engage tracks in different planes than oneanother. As with the expander, the tracks also may be at various anglesto the longitudinal axis of the implant including parallel with thelongitudinal axis of the implant. Other means for respectively engagingthe implants and the expander position thereof are anticipated andwithin the scope of the present invention.

[0079] In rotating the expander, the longer dimension of the expander issubstituted for the lesser dimension of the expander thuscorrespondingly increasing the maximum height of the implant from thefirst to the second position. As best shown in FIG. 9, the schematicrepresentation of a geometric configuration of a cross-section of anexpander 122 in accordance with one embodiment of the present invention,includes: a first dimension X corresponding to the height of expander122 when implant 100 is initially inserted into the spine and to thewidth of expander 122 when expander 122 is rotated to increase height Hof implant 100; and a second dimension Y corresponding to the width ofexpander 122 when implant 100 is initially inserted into the spine andto the height of expander 122 when expander 122 is rotated to increaseheight H of implant 100. Second dimension Y is greater than firstdimension X. Expander 122 has an upper surface 136, a lower surface 138,and side surfaces 140 as defined when expander 122 is positioned afterrotation to increase height H of implant 100. As used herein, the term“side surfaces” refers to those portions of expander 122 that extendfrom upper member 102 to lower members 106 after expander 122 has beenrotated into its final deployed, or second position to increase theheight H of implant 100. The “upper” and “lower” surfaces refer to thoseportions of expander 122 that are in contact with upper and lowermembers 102, 106 when implant 100 is in its second position andconfiguration and is fully expanded.

[0080] A preferred expander 122 is in the form of a modified rectangleor rhomboid. The expander generally has a longer dimension Y and ashorter dimension X. When the expander is inserted into a firstposition, the short dimension X spans the distance between upper to thelower members 102, 106 and when expander 122 is in the second position,the longer dimension Y of expander 122 spans the distance between upperand lower members 102, 106.

[0081] Expander 122 in one embodiment of the present embodiment has across-section with side surfaces 140 interesting upper and lowersurfaces 136, 138 at two junctions which may be diametrically opposedcorners 142 and two diametrically opposed arcs 144. Arcs 144 arepreferably each of the same radius and the modified hypotenuse MHbetween opposed arcs 144 generally approximates the distance betweenupper and lower surfaces 136, 138 such that, when expander 122 isrotated from an initial insertion position toward a final deployedposition, no substantial over-distraction occurs between adjacentvertebral bodies V.

[0082] The modified hypotenuse MH of this embodiment of the presentinvention may be equal, slightly less than, or slightly greater thandimension Y of expander 122. Having the modified hypotenuse MH beslightly greater than the dimension Y offers the advantage of havingexpander 122 stabilized by an over-center position, such that moreenergy would be required to derotate the expander than for it to remainin the deployed or second position. By “without substantialover-distraction” what is meant is that the modified hypotenuse MHlength is closer to the expander dimension Y than to the unmodifiedhypotenuse UH; and is selected to allow the implant to preferablyoperate in the range of elastic deformation of the tissues about theoperated disc space. Corners 142 may form, but not necessarily, a90-degree angle and have an unmodified hypotenuse dimension UH.

[0083] By way of example, consider one embodiment of expandable implant100 of the present invention having an optimum expanded height of 18 mmfor a given implantation space. Any implant bigger than 18 mm should notbe used in this implantation space because during expansion of theimplant, its height would move through the range of elastic deformationof the surrounding tissues and after that the implant would crush thevertebral bone or tear ligaments. Inserting an expander such that whenthe implant is fully expanded allows the implant to be 18 mm would beideal. It may be that an implant having a 17.5 mm expanded height forthis implantation space is nearly as good, but a 16 mm expanded heightmay be too short to fit tightly within the implantation space. Using apreferred rectangular expander without any modification to thehypotenuse that is adapted to expand the implant to the optimum 18 mmfinal height would require the expander to have a hypotenuse causing theimplant to exceed the 18 mm expanded height temporarily during rotationof the expander. So turning the expander without a modified hypotenusewould break the vertebrae or tear the ligaments. In reverse, if onecould not expand the implant to more than 18 mm without causing damageto the spine, then an implant selected to have an expander having a fullunmodified hypotenuse so as to upon rotation temporarily cause theimplant height to be 18 mm would in the finally expanded position allowthe implant height to collapse such that there would be insufficientheight for the implant to adequately distract the implantation space.Generally, the modified hypotenuse of the expander is closer in lengthto dimension Y of the expander than to the unmodified hypotenuse.

[0084] As best shown in FIG. 1 in this particular embodiment, expander122 has a depth dimension Z that is less than that of first and seconddimensions Y, X. Expander 122 of the present embodiment has a fixedshape during movement from initial-insertion position I to finaldeployed position F within implant 100.

[0085] As shown in FIGS. 22A, 22B, and 23, blocker 121 may also take theform of a trailing wall that articulates or hinges to the inside ofimplant 100. The trailing wall may be left open during insertion ofimplant 100 so as to trail behind the upper and lower members. Thetrailing wall does not protrude outside of a projection rearward of thecircumference of implant 100. Once implant 100 is implanted intoposition, the trailing wall is rotated about one of its ends and pushedinto position and locked into place. This may occur by having thetrailing wall contact an inclined plane that leads up to a notch intowhich the trailing wall locks into place. The trailing wall itself mayalso have at least one opening in it to permit the further loading offusion-promoting materials into implant 100.

[0086] While modified hypotenuse MH is illustrated as being between arcs144 in this preferred embodiment, the configuration of expander 122 toform modified hypotenuse MH can take many forms, such that thosejunctions are relieved so as to have the desired lesser dimensiontherebetween, including arcs, chamfers, a series of angled surfaces, orany other shape so long as the modified hypotenuse MH is sufficientlyreduced in dimension to function for the intended purpose according tothe present teaching.

[0087] An embodiment of the present invention where modified hypotenuseMH is slightly greater than height Y offers the advantage of anover-center effect that locks expander 122 into place. In this instance,once expander 122 rotates past the diagonal of the modified hypotenuseMH, more force would be required to rotate it back from the finaldeployed position to its insertion position than in an embodiment wheremodified hypotenuse MH is equal to or less than height Y. Preferably,expander 122 offers a surgeon multiple sensory advantages including: thetactile feel of expander 122 going over center and locking into place;the visual of the handle of a tool rotating expander 122 such that thetool handle goes from perpendicular to parallel, the reverse, or other,to the disc space into place; and auditory from the sound of expander122 snapping into place.

[0088] Each of upper and lower surfaces 136, 138 of expander 122 of thepresent embodiment lie generally in a plane and are generally parallelto one another. For any implant it is anticipated that a physician maybe able to select from a series of blockers or expanders allowing forvarying the increase in the implant height. Side surfaces 140 and upperand lower surfaces 136, 138 are oriented so as to substantially form aparallelogram. Any of a number of configurations for the expander forincreasing the height of the implant is possible, based on the teachingsof the present application and such configurations as would be known toone of skill in the art are anticipated within the scope of the presentinvention.

[0089] The implant may preferably have an overlapping step-cut walljunction between upper and power members 102, 106 which offers theadvantage of increasing the lateral rigidity of implant 100 holding theimplant in the closed first position until expanded, and to the extentdesired retaining the fusion-promoting materials within. The walljunction may be either solid or perforated. As best shown in FIG. 1,upper member 102 in one embodiment of the preferred invention hasinterior walls 146 extending from each side of arcuate portion 104toward lower member 106. Interior wall 146 is aligned parallel tolongitudinal axis L of implant 100. Lower member 106 has aninterior-contacting surface 148 adapted to contact or receive interiorwall 146.

[0090] In a preferred embodiment, upper and lower members 102, 106 arearticulated to one another so one of the respective ends of upper andlower members 102, 106 remain articulated while the other of therespective ends of upper and lower members 102, 106 are free to moveaway from one another. In a preferred embodiment the articulating meansis achieved without a third member such as an axle shaft passing throughthe implant. The articulating means preferably is formed into theimplant walls themselves in such a way that the two implant halves maybe articulated when the halves are at 90 degrees to each other and thenthe halves are moved toward each other for insertion into theimplantation space in the spine. The two halves are closed much like thecover of a book. The halves are locked together such thatdisarticulation will not occur when the implant is assembled for use.Any of a number of ways of articulating or joining upper and lowermembers 102, 106 is possible.

[0091] As best shown in FIG. 1 in this embodiment, upper and lowermembers 102, 106 of the present embodiment have a pivot point betweenadjacent distal ends 126 or leading ends 150 of upper and lower members102, 106. The pivot point in the present embodiment is at the end ofimplant 100 opposite expander 122. The pivot point of the presentembodiment operates as a hinge or axle 152 but is formed out of thewalls themselves so as to preferably not intrude into the implantinterior or hollow or to block access thereto. Hinge 152 includes aprojection 154 extending radially from each side of arcuate portion 108of lower member 106 and a slotted bracket 156 extending from each sideof arcuate portion 104 of upper member 102 for engaging projection 154.Brackets 156 and projections 154 are configured such that engagementoccurs when upper and lower members 102, 106 are substantiallyperpendicular to one another. Brackets 156 and projections 154 areconfigured so as not to disengage within a range of movement of upperand lower members 102, 106 that would occur when the implant is in useeither during insertion or resulting from the expansion in height ofimplant 100.

[0092] As best shown in FIG. 11, interior wall 146 of upper member 102of the present embodiment is unexposed when implant 100 is in initialinsertion position 1. As shown in FIG. 12C, when implant 100 is in theexpanded position F, implant 100 has a shape such that each of arcuateportions 104, 108 of upper and lower members 102, 106 are separated byat least a portion of interior wall 146, which in this position has anexposed side. The exposed side of the present embodiment is smooth andflat.

[0093] As best shown in FIG. 8, a cap 158 having an exterior surface 160and an interior surface 162 is used to close leading end 150 of implant100. Interior surface 162 of cap 158 has spaced slots 164 about itscircumference to facilitate a snap fit between cap 158 and implant 100.Cap 158 and implant 100 can of course be adapted for either or both endsof implant 100.

[0094] As discussed above, implant 100 has a leading end 150 and atrailing end 126. One of the ends preferably has a tool-engagingportion. This tool-engaging portion is adapted to engage an insertiontool that holds and rotates implant 100 into position. The tool-engagingconfiguration may be an opening, and more particularly an opening thatis along the longitudinal axis of the implant to facilitate the use ofan insertion tool that rotates implant 100 into an inserted position. Ofcourse, the tool-engaging portion need not be an opening. A hole or ablind hole, threaded or otherwise, is preferred in another embodiment.In another preferred embodiment the opening preferably is a threadedslot that functions to cooperatively engage and disengage a tool for usein inserting implant 100. The opening either alone on the proximal endof implant 100 or in conjunction with other openings on the proximal endfunction to hold fusion-promoting material in implant 100 whilepermitting vascular access and bone growth through the opening oropenings.

[0095] Implants of the present invention may have an end adapted tocooperatively engage an implant driver. The anterior approach implantmay have a leading end, trailing end, or both ends that are adapted toengage a cap. One of the purposes for that cap includes restricting thepassage of fusion-promoting substances so that they remain loaded withinthe implant. Another purpose of the cap may be to add structural supportto the implant. The cap may be solid or it may have openingstherethrough. Any such openings could allow for the loaded material tostay within the implant while providing for vascular access to allow forthe ingrowth of blood vessels and the growth of bone through the end ofthe implant.

[0096] For a posterior approach implant the cap may be on either or bothends. The trailing end of the implant in a posterior approach implanthas direct exposure to the spinal canal where the spinal cord and nerveroots are located. A cap on a posterior approach implant may be for thepurpose of sealing off the spinal canal from the fusion-promotingsubstances contained in the hollow interior of the implant so that nobone grows into the canal. Further, the present invention implant may beused in combination with chemical substances and/or compounds applied atthe trailing end of the implant to inhibit scar formation, and the capmay be of benefit in shielding the fusion-promoting substances containedin the implant from these scar formation inhibiting chemicals andcompounds. It may also be for the purposes identified herein used inassociation with the leading end cap of an anterior approach implant.

[0097] Shown in FIGS. 14-16, in accordance with the present invention,as embodied and broadly described herein, is a second embodiment of anexpandable threaded artificial interbody spinal fusion implant 200 forposterior insertion across a disc space D between two adjacent vertebralbodies V of a human spine. Threaded implant 200 of the present inventionincludes an upper member 202 having an arcuate portion 204 adapted forplacement toward and at least in part within the upper of the adjacentvertebral bodies V and a lower member 206 having an arcuate portion 208adapted for placement toward and at least in part within the lower ofthe adjacent vertebral bodies V. Implant 200 in FIGS. 14 and 15 is shownbeing implanted into the spine from the posterior aspect with expander222 on the distal end 226 or leading end 250 of implant 200. Whileanterior and posterior aspect approaches have been illustrated herein,the present invention is not limited to these illustrated approaches. Inparticular, but not limited thereto, the threaded implant of the presentinvention also may be used in threaded implants for insertion from thetranslateral aspect of the spine as disclosed by Michelson in U.S. Pat.No. 5,860,973, which is incorporated herein by reference.

[0098] As best shown in FIG. 16, tracks 232, 234 of upper and lowermembers 202, 206 of the second embodiment have a cooperating surface 266and expander 222 has a corresponding cooperating surface 268 thatcontacts cooperating surface 266 of tracks 232, 234 to orient expander222 in a predetermined location. The cooperating surfaces orientexpander 222 within implant 200 such that the axis of rotation ofexpander 222 is parallel to the longitudinal axis of implant 200 andmore particularly center expander 222 within implant 200 such that theaxis of rotation of expander 222 coincides with longitudinal axis L ofimplant 200.

[0099] Tracks 232, 234 include sides 270 having cooperating surface 266and expander 222 has corresponding cooperating surface 268 used toorient expander 122 in a predetermined location. Cooperating surface 266of side 270 is a detent and corresponding cooperating surface 268 ofexpander 222 is a projection. The projection preferably projects awayfrom expander 222 in a direction parallel to the longitudinal axis ofimplant 200. The detent and the projection preferably center expander222 within implant 200 such that the axis of rotation of expander 222coincides with the longitudinal axis of implant 200.

[0100] Shown in FIGS. 17-19, in accordance with the present invention,as embodied and broadly described herein, is a third embodiment of anexpandable threaded artificial interbody spinal fusion implant 300 forinsertion across a disc space D between two adjacent vertebral bodies Vof a human spine. Threaded implant 300 of the present invention includesan upper member 302 having an arcuate portion 304 for orientation towardthe upper of adjacent vertebral bodies V and a lower member 306 havingan arcuate portion 308 for orientation toward the lower of the adjacentvertebral bodies V.

[0101] Implant 300 of the present embodiment may include any of thevarious features disclosed in association with implant 100 and implant200 disclosed herein. Implant 300 further includes a side surface 372contoured to cooperatively receive another implant. See U.S. Pat. No.5,593,409 by Michelson for a discussion of the advantages associatedwith placing implants in side-in-side contact.

[0102] Another aspect of implant 300 is that its upper and lower members302, 306 have screw holes 374 passing therethrough adapted to receive ascrew 378 passing from the interior of implant 300 into adjacentvertebral bodies V to anchor implant 300 to an adjacent vertebral bodyV.

[0103] The articulation may be of one of two general types, examples ofwhich are each herein disclosed. As shown in previously describedembodiments of the present invention, the articulation may allowrotation about the articulation. A second type of articulation allowsfor both rotation and expansion at the point of articulation. An exampleof this is shown in FIG. 19, where a peg and hook design is utilized.While in this example both functions, that is rotation or pivoting, andcaptured or limited expansion with a fixed end point or stop, occur atthe same location. Alternatively, and without departing from theteachings of the present invention, those functions can be divided. Byway of example only, and not limitation, expansion can be allowed andcontrolled by an interlocking wall design, as shown by the interlockingmembers in the alternative embodiments of FIGS. 20 and 21. Various otherstructural features as would be obvious to one of ordinary skill in theart after the teachings herein can similarly be employed.

[0104] A fixed end point for the implant expansion is preferred for theproper functioning of the opposed bone screws. A purpose of the opposedbone screws is to rigidly secure the implant within the vertebralsegment. A further purpose is to pull each of the adjacent vertebralbodies toward the implant and towards each other so as to have aconstruct resistant to the deleterious effects of vertebral rocking asmay otherwise occur with spinal flexion and extension absent suchrestraint. If the articulation device captured the upper and lowermembers together, as in the embodiments of FIGS. 1-16, by closelyencircling a post then the implant could not expand at that location. Sothe coupling mechanism of FIG. 19 permits the upper and lower members toremain articulated, permits the implant to expand, and permits thescrews to pull against the implant and each other, in oppositedirections and to pull the bones toward each other. The optionalextended slot and peg configuration on the right-hand side of FIG. 19illustrated in dashed image lines is not needed to hold the implanttogether.

[0105] In accordance with this embodiment of the present invention, asecond expander may be located at least in part between the upper andlower members for moving at least a portion of the upper and lowermembers away from one another to increase the height of the implantdefined by the maximum distance between the arcuate portions of theupper and lower members. All of the features described herein for theexpander may also be applicable to the second expander. Additionally,the second expander may be located proximate an end of the implantopposite the other expander, thereby providing an implant capable ofbeing expanded at both ends of implant. The increased height of theimplant resulting from moving the two expanders may be the constant orvaried along the length of the implant according to the desiredconfiguration of the implant.

[0106] The expandable threaded spinal fusion implant may be made ofartificial or naturally occurring materials suitable for implantation inthe human spine. The implant can comprise bone including, but notlimited to, cortical bone. The implant can also be formed of materialother than bone, such as metal including, but not limited to, titaniumand its alloys or ASTM material, surgical grade plastics, plasticcomposites, ceramics, or other materials suitable for use as a threadedspinal fusion implant. The plastics may be bioresorbable. The threadedspinal fusion implant of the present invention can further be formed ofbone growth promoting materials, including but not limited to, bonemorphogenetic proteins, hydroxyapatite, and genes coding for theproduction of bone. The threaded implant can be treated with a bonegrowth promoting substance, can be a source of osteogenesis, or can beat least in part bioabsorbable. The threaded implant of the presentinvention can be formed of a porous material.

[0107] The expandable threaded spinal fusion implant of the presentinvention may be coated with, comprised of, be used in combination with,or have a hollow for containing bone growth promoting materials,including but not limited to, bone morphogenetic proteins,hydroxyapatite, and genes coding for the production of bone. Thethreaded spinal fusion implant of the present invention can be formed ofa material that intrinsically participates in the growth of bone fromone of adjacent vertebral bodies V to the other of adjacent vertebralbodies V.

[0108] While various embodiments of the present invention are presentedby way of example only and not limitation, common to each of them, isthat the expandable threaded spinal fusion implant for insertion acrossdisc space D between two adjacent vertebral bodies V of a human spinehas an upper member having an arcuate portion adapted for placementtoward and at least in part within the upper of the adjacent vertebralbodies V. The implant also has a lower member having an arcuate portionadapted for placement toward and at least in part within the lower ofthe adjacent vertebral bodies V. The arcuate portions of the upper andlower members have at least one opening. The openings of the upper andlower members are in communication with one another to permit for thegrowth of bone from vertebral body V to adjacent vertebral body Vthrough the implant. At least a portion of a thread for engagingadjacent vertebral bodies V is on the exterior of each of the opposedarcuate portions of the upper and lower members. A blocker in the formof an expander preferably is located proximate at least one of the endsto hold at least a portion of the upper and lower members apart from oneanother to increase the implant height.

[0109] There is disclosed in the above description and the drawingsimplants, which fully and effectively accomplish the objectives of thisinvention. However, it will be apparent that variations andmodifications of the disclosed embodiments may be made without departingfrom the principles of the invention or the scope of the appendedclaims.

What is claimed is:
 1. A threaded interbody spinal fusion implant for at least in part rotational insertion across a disc space between two adjacent vertebral bodies of a spine, said implant comprising: an upper member having a portion being at least in part arcuate adapted for placement toward and at least in part within one of the adjacent vertebral bodies, said upper member having at least one opening adapted to communicate with one of the adjacent vertebral bodies, said upper member having a proximal end and a distal end; a lower member having a portion being at least in part arcuate adapted for placement toward and at least in part within the other of the adjacent vertebral bodies, said lower member having at least one opening adapted to communicate with the other of the adjacent vertebral bodies, said openings of said upper and lower members being in communication with one another and adapted for permitting for the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant and being sufficiently sized and located to allow for interbody spinal fusion through said implant, said lower member having a proximal end and a distal end corresponding to said proximal end and said distal end of said upper member, respectively, and a length between said proximal and distal ends, said upper and lower members articulating therebetween adjacent one of said proximal ends and said distal ends of said upper and lower members and allowing for expansion of the height of said implant, said upper and lower members having a first position relative to one another allowing for a collapsed implant height and a second position relative to one another allowing for an increased height, said arcuate portions of said upper and lower members in the first position being parallel to one another over a substantial portion of the length of said implant and forming at least a portion of a cylinder along the length of said implant; at least a portion of a helical thread formed on the exterior of each of said opposed arcuate portions of said upper and lower members for penetrably engaging the adjacent vertebral bodies and to facilitate securing said implant into the spine by at least in part rotating said implant about the longitudinal axis of said implant; and at least one blocker adapted to cooperatively engage and hold at least a portion of said upper and lower members apart so as to maintain the increased height of said implant and resist the collapse of said implant to the collapsed implant height when said implant is in a final deployed position.
 2. The threaded implant of claim 1, further comprising a hollow defined between said upper and lower members in communication with said openings in each of said upper and lower members, said hollow being adapted to receive fusion-promoting substances.
 3. The threaded implant of claim 2, wherein said hollow has a width that is unobstructed by any mechanism for moving said blocker.
 4. The threaded implant of claim 2, further comprising a second hollow between said upper and lower member located between said blocker and said end of said implant proximate said blocker.
 5. The threaded implant of claim 3, wherein said implant has a constant width in both the collapsed height and the increased height.
 6. The threaded implant of claim 3, wherein said blocker is located at least in part between said upper and lower members.
 7. The threaded implant of claim 3, wherein said blocker is located at a predetermined location along the length of said implant and remains at the predetermined location in transitioning said implant from said first position to said second position.
 8. The threaded implant of claim 3, wherein said blocker is located proximate at least one of said ends of said upper and lower members.
 9. The threaded implant of claim 3, wherein said blocker is adapted to cooperatively engage a tool used to move said blocker from an initial position to a final position to increase the height of said implant, said tool not being a part of said implant and being removed from said implant after moving said blocker into the final position.
 10. The threaded implant of claim 3, wherein said implant has a width and said blocker has a width less than the width of said implant.
 11. The threaded implant of claim 3, wherein said implant has side walls and said blocker does not contact said side walls when said implant is in the final deployed position.
 12. The threaded implant of claim 3, wherein each of said upper and lower members are adapted to cooperate with and to fixedly locate said blocker.
 13. The threaded implant of claim 12, wherein each of said upper and lower members have a track configured to permit said blocker to seat therein.
 14. The threaded implant of claim 13, wherein at least one of said tracks and said blocker are adapted to cooperate with each other to center said blocker along a longitudinal axis of said implant.
 15. The threaded implant of claim 3, wherein said blocker moves said arcuate portions of said upper and lower members from a parallel orientation to an angled orientation relative to one another.
 16. The threaded implant of claim 3, further comprising a second blocker located between said upper and lower members for holding at least a portion of the upper and lower members apart where said second expander is located.
 17. The threaded implant of claim 3, wherein said blocker is an expander adapted to expand said implant from a first collapsed height to a second expanded height when moved from a first to a second position.
 18. The threaded implant of claim 17, wherein said implant has a longitudinal axis and said expander rotates in a plane generally perpendicular to the longitudinal axis of said implant to increase the height of said implant.
 19. The threaded implant of claim 17, wherein said expander is located along the length of said implant.
 20. The threaded implant of claim 17, wherein said expander is located proximate said proximal ends of said upper and lower members.
 21. The threaded implant of claim 17, wherein said expander is located proximate said distal ends of said upper and lower members.
 22. The threaded implant of claim 17, further comprising a hollow defined between said upper and lower members in communication with said openings in each of said upper and lower members, said hollow being adapted to receive fusion-promoting substances, said hollow being substantially unobstructed by said expander extending along a substantial portion of the length of said hollow so as to permit growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 23. The threaded implant of claim 17, wherein said expander remains in the same location along the longitudinal axis of the implant when rotated.
 24. The threaded implant of claim 17, wherein said expander is located at a predetermined location along the length of said implant and remains so located in transitioning said implant from the first position to the second position.
 25. The threaded implant of claim 17, wherein said expander is adapted to cooperatively engage a tool used to move said expander from an initial position to a final position to increase the height of said implant, said tool not being a part of said implant and being removed from said implant after moving said expander into the final position.
 26. The threaded implant of claim 17, wherein said expander is adapted to cooperatively engage a tool that rotates about an axis parallel to the longitudinal axis of said implant to rotate said expander to increase the height of said implant.
 27. The threaded implant of claim 26, wherein said expander rotates in a plane perpendicular to the longitudinal axis of said implant to increase the height of said implant.
 28. The threaded implant of claim 27, wherein said expander remains in the same location along the longitudinal axis of the implant when rotated.
 29. The threaded implant of claim 17, wherein said expander moves said arcuate portions of said upper and lower members from a parallel orientation to an angled orientation relative to one another.
 30. The threaded implant of claim 17, wherein each of said upper and lower members are adapted to cooperate with said expander.
 31. The threaded implant of claim 30, wherein each of said upper and lower members have a track configured to permit said expander to rotate therein.
 32. The threaded implant of claim 31, wherein said tracks permit said expander to move from side to side within said track.
 33. The threaded implant of claim 30, wherein said track of said upper member and said track of said lower member are in the same plane.
 34. The threaded implant of claim 30, wherein said track of said upper member and said track of said lower member are parallel to one another.
 35. The threaded implant of claim 30, where said track of said upper member and said track of said lower member are in a plane perpendicular to the longitudinal axis of said implant.
 36. The threaded implant of claim 17, wherein said upper and lower members structurally cooperate with said expander so as to keep said expander located within said implant.
 37. The threaded implant of claim 30, wherein at least one of said tracks of said upper and lower members has a cooperating surface, said expander having a corresponding cooperating surface that contacts said cooperating surface of said at least one track to orient said expander in a predetermined location.
 38. The threaded implant of claim 37, wherein said cooperating surfaces orient said expander within said implant such that the axis of rotation of said expander is parallel with the longitudinal axis of said implant.
 39. The threaded implant of claim 38, wherein said cooperating surfaces center said expander within said implant such that the axis of rotation of said expander coincides with the longitudinal axis of said implant.
 40. The threaded implant of claim 3, wherein said upper and lower members are configured to cooperate with one another so as to stop said upper and lower members from being moved apart from one another more than a predetermined distance.
 41. The threaded implant of claim 30, wherein said upper and lower portions are adapted to cooperate with said expander so as to center said expander within a cross section of the upper and lower portions.
 42. The threaded implant of claim 30, wherein at least one of said tracks of said upper and lower members includes at least one side having a cooperating surface, said expander having a corresponding cooperating surface that contacts said cooperating surface of said at least one side to orient said expander in a predetermined location.
 43. The threaded implant of claim 42, wherein said cooperating surface of said at least one side is a detent and said corresponding cooperating surface of said expander is a projection.
 44. The threaded implant of claim 43, wherein said detent and said projection center said expander within said implant such that the axis of rotation of said expander coincides with the longitudinal axis of said implant.
 45. The threaded implant of claim 17, wherein said expander has a first height corresponding to the height of said expander when said implant is initially inserted into the spine, said expander having a second height corresponding to the height of said expander when said expander is moved into a final deployed position to increase the height of said implant, said second height being greater than said first height.
 46. The threaded implant of claim 17, wherein said expander has an upper surface, a lower surface, and side surfaces as defined when said expander is positioned to increase the height of said implant, said side surfaces intersecting said upper and said lower surfaces at two diametrically opposed junctions.
 47. The threaded implant of claim 46, wherein said two diametrically opposed junctions are a pair of diametrically opposed corners and a pair of diametrically opposed arcs
 48. The threaded implant of claim 46, wherein each of said upper and lower surfaces lie generally in a plane.
 49. The threaded implant of claim 46, wherein said upper and lower surfaces are generally parallel to one another.
 50. The threaded implant of claim 46, wherein said side surfaces and said upper and lower surfaces are oriented to substantially form a parallelogram.
 51. The threaded implant of claim 45, wherein the difference between said first height and said second height of said expander approximates the difference in height of said implant between said first position and said second position as measured proximate the location of said expander.
 52. The threaded implant of claim 47, wherein said two diametrically opposed arcs are each of the same radius.
 53. The threaded implant of claim 52, wherein the distance across said two diametrically opposed arcs generally approximates the distance between said upper and lower surfaces of said expander.
 54. The threaded implant of claim 47, wherein said two diametrically opposed corners form a 90-degree angle.
 55. The threaded implant of claim 17, wherein said expander has a depth dimension less than that of said first and second height of said expander.
 56. The threaded implant of claim 55, wherein said expander has a fixed shape during movement from an initial insertion position to a final deployed position within said implant.
 57. The threaded implant of claim 17, further comprising a second expander located between said upper and lower members for moving at least a portion of the upper and lower members away from one another to increase the maximum height of said implant where said second expander is located.
 58. The threaded implant of claim 57, wherein said second expander rotates to increase the height of said implant.
 59. The threaded implant of claim 57, wherein said second expander is located proximate an end of said implant opposite said expander.
 60. The threaded implant of claim 57, wherein said implant has a longitudinal axis and said second expander rotates in a plane perpendicular to the longitudinal axis of said implant to increase the height of said implant.
 61. The threaded implant of claim 59, wherein said hollow is substantially unobstructed by said second expander extending along a substantial portion of the length of said hollow so as to permit growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 62. The threaded implant of claim 59, wherein said second expander remains in the same location along the longitudinal axis of the implant when rotated.
 63. The threaded implant of claim 57, wherein said second expander is located proximate one of the proximal end and the distal end of said upper and lower members.
 64. The threaded implant of claim 63, wherein said hollow is unobstructed by said second expander extending along a substantial portion of the length of said hollow to permit growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 65. The threaded implant of claim 63, further comprising a second hollow between said upper and lower member located between said second expander and said end of said implant proximate said second expander.
 66. The threaded implant of claim 57, wherein each of said upper and lower members have a track within which said second expander rotates.
 67. The threaded implant of claim 55, wherein said track is configured to permit said second expander to rotate therein and then to move from side to side within said track.
 68. The threaded implant of claim 57, wherein said second expander has a first height corresponding to the height of said second expander when said implant is initially inserted into the spine, said second expander having a second height corresponding to the height of said second expander when said second expander is moved into a final deployed position to increase the height of said implant, said second height being greater than said first height.
 69. The threaded implant of claim 57, wherein said second expander has an upper surface, a lower surface, and side surfaces as defined when said second expander is positioned to increase the height of said implant, and said side surfaces intersecting said upper and said lower surfaces at two diametrically opposed junctions.
 70. The threaded implant of claim 69, wherein the difference between said first height and said second height of said second expander approximates the difference in height of said implant between said first position and said second position as measured proximate the location of said second expander.
 71. The threaded implant of claim 3, wherein said upper and lower members have walls contacting one another.
 72. The threaded implant of claim 71, wherein said walls are aligned parallel with the longitudinal axis of said implant.
 73. The threaded implant of claim 71, wherein said walls are at least in part overlapping.
 74. The threaded implant of claim 3, wherein said upper and lower members have a rotational articulation therebetween adjacent one of said proximal end and said distal end of said upper and lower members.
 75. The threaded implant of claim 74, wherein said rotational articulation is at one of said proximal end and said distal end of said upper and lower members opposite said blocker.
 76. The threaded implant of claim 74, wherein said rotational articulation allows for expansion.
 77. The threaded implant of claim 76, wherein said rotational articulation allows for limited expansion.
 78. The threaded implant of claim 74, wherein said rotational articulation is formed by said upper and lower members interdigitating so as to cooperatively engage.
 79. The threaded implant of claim 78, wherein said rotational articulation is configured such that engagement occurs when said upper and lower members are substantially perpendicular to one another.
 80. The threaded implant of claim 79, wherein said rotational articulation is configured to remain engaged within a range of movement of said upper and lower members resulting from positioning said implant in the second position.
 81. The threaded implant of claim 3, wherein one of said upper and lower members has an interior wall, which is unexposed, extending therefrom toward the other of said upper and lower members when said implant is in an initial insertion position, and when said implant is in a final position said implant has a shape such that each of said arcuate portions of said upper and lower members are separated by at least a portion of said interior wall, which now has an exposed side.
 82. The threaded implant of claim 81, wherein said upper and lower members have side walls for engaging each other.
 83. The threaded implant of claim 82, wherein said side walls of said upper and lower members are at least partially overlapping walls.
 84. The threaded implant of claim 81, wherein said arcuate portions of said upper and lower members form an angular orientation relative to one another when said implant is in the final position.
 85. The threaded implant of claim 81, wherein said arcuate portions of said upper and lower members when said implant is in the initial insertion position form a cylindrical shape.
 86. The threaded implant of claim 3, wherein said implant has an interior, at least one of said upper and lower members has a screw hole passing therethrough adapted to receive a screw passing from said interior of said implant into one of the adjacent vertebral bodies.
 87. The threaded implant of claim 86, wherein each of said upper and lower members has at least one screw hole passing therethrough adapted to receive a screw passing from said interior of said implant into the adjacent vertebral body in contact with each of said upper and lower members respectively.
 88. The threaded implant of claim 86, further comprising at least one screw adapted to pass from said interior of said implant through said screw hole and into the adjacent vertebral body to anchor said implant to the adjacent vertebral body.
 89. The threaded implant of claim 3, wherein said implant has a side surface when in a final position that is contoured to cooperate with another implant.
 90. The threaded implant of claim 89, wherein said implant and said cooperating other implant have a combined width therebetween less than the combined height of said implant and said cooperating other implant.
 91. The threaded implant of claim 3, further comprising a cap for closing one of said proximal end and said distal end of said upper and lower members, said cap having an exterior surface and an interior surface.
 92. The threaded implant of claim 91, wherein said interior surface of said cap has spaced slots about its circumference to facilitate a snap fit of said cap into said implant.
 93. The threaded implant of claim 3, wherein said implant comprises an artificial material other than bone.
 94. The threaded implant of claim 3, wherein said implant is made of an artificial material that is stronger than bone.
 95. The threaded implant of claim 3, wherein said implant is made of an artificial material that is harder than bone.
 96. The threaded implant of claim 3, wherein said implant comprises bone.
 97. The threaded implant of claim 96, wherein said bone includes cortical bone.
 98. The threaded implant of claim 3, wherein said implant comprises bone growth promoting material.
 99. The threaded implant of claim 98, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.
 100. The threaded implant of claim 3, wherein said implant is treated with a bone growth promoting substance.
 101. The threaded implant of claim 3, wherein said implant is a source of osteogenesis.
 102. The threaded implant of claim 3, wherein said implant is at least in part bioabsorbable.
 103. The threaded implant of claim 3, wherein said implant comprises metal.
 104. The threaded implant of claim 103, wherein said metal is ASTM material suitable for use said threaded spinal fusion implant.
 105. The threaded implant of claim 103, wherein said metal includes titanium.
 106. The threaded implant of claim 3, wherein said implant comprises a plastic material.
 107. The threaded implant of claim 3, wherein said implant comprises a ceramic material.
 108. The threaded implant of claim 3, wherein said implant is formed of a porous material.
 109. The threaded implant of claim 3, wherein said implant is formed of a material that intrinsically participates in the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 110. The threaded implant of claim 3, wherein said implant has an interior surface and a hollow defined therein, said hollow being capable of containing bone growth promoting material.
 111. The threaded implant of claim 110, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.
 112. The threaded implant of claim 3, wherein said at least one opening is adapted to retain fusion-promoting materials
 113. The threaded implant of claim 3, wherein at least a portion of said implant is treated to promote bone ingrowth between said implant and said adjacent vertebral bodies.
 114. The threaded implant of claim 3, in combination with a chemical substance to inhibit scar formation.
 115. The threaded implant of claim 3, wherein said blocker is an expander having an external thread, each of said upper and lower members having a threaded converging portion adapted to cooperate with said external thread of said expander to expand said implant from a first collapsed height to a second expanded height when said expaner is rotated from a first to a second position.
 116. A threaded interbody spinal fusion implant for at least in part rotational insertion across a disc space between two adjacent vertebral bodies of a spine, said implant comprising: an upper member having a portion being at least in part arcuate adapted for placement toward and at least in part within one of the adjacent vertebral bodies, said upper member having at least one opening adapted to communicate with one of the adjacent vertebral bodies, said upper member having a proximal end and a distal end; a lower member having a portion being at least in part arcuate adapted for placement toward and at least in part within the other of the adjacent vertebral bodies, said lower member having at least one opening adapted to communicate with the other of the adjacent vertebral bodies, said openings of said upper and lower members being in communication with one another and adapted for permitting for the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant and being sufficiently sized and located to allow for interbody spinal fusion through said implant, said lower member having a proximal end and a distal end corresponding to said proximal end and said distal end of said upper member, respectively, and a length between said proximal and distal ends, said upper and lower members articulating therebetween adjacent one of said proximal ends and said distal ends of said upper and lower members and allowing for expansion of the height of said implant, said upper and lower members having a first position relative to one another allowing for a collapsed implant height and a second position relative to one another allowing for an increased height, said arcuate portions of said upper and lower members in the first position being parallel to one another over a substantial portion of the length of said implant and forming at least a portion of a cylinder along the length of said implant; at least a portion of a helical thread formed on the exterior of each of said opposed arcuate portions of said upper and lower members for penetrably engaging the adjacent vertebral bodies and to facilitate securing said implant into the spine by at least in part rotating said implant about the longitudinal axis of said implant; and a blocker pivotally attached to one of said upper and lower members proximate one of said proximal and distal ends and being adapted to pivot into cooperative engagement with another of said one of said upper and lower members, said blocker being adapted to hold at least a portion of said upper and lower members apart so as to maintain the increased height of said implant and resist the collapse of said implant to the collapsed implant height when said implant is in a final deployed position, said implant having a width and said blocker having a width less than the width of said implant.
 117. The threaded implant of claim 116, further comprising a hollow defined between said upper and lower members in communication with said openings in each of said upper and lower members, said hollow being adapted to receive fusion-promoting substances.
 118. The threaded implant of claim 117, wherein said hollow has a width that is unobstructed by any mechanism for moving said blocker.
 119. The threaded implant of claim 117, wherein said implant has a constant width in both the collapsed height and the increased height.
 120. The threaded implant of claim 117, wherein said blocker is located at least in part between said upper and lower members.
 121. The threaded implant of claim 117, wherein said blocker is located at a predetermined location along the length of said implant and remains at the predetermined location in transitioning said implant from said first position to said second position.
 122. The threaded implant of claim 117, wherein said blocker is a portion of one of said ends of said upper and lower members.
 123. The threaded implant of claim 117, wherein said blocker is adapted to cooperatively engage a tool used to move said blocker from an initial position to a final position to increase the height of said implant, said tool not being a part of said implant and being removed from said implant after moving said blocker into the final position.
 124. The threaded implant of claim 117, wherein said blocker has a width less than one half the width of said implant.
 125. The threaded implant of claim 117, wherein said implant has side walls and said blocker does not contact said side walls when said implant is in the final deployed position.
 126. The threaded implant of claim 117, wherein said blocker moves said arcuate portions of said upper and lower members from a parallel orientation to an angled orientation relative to one another.
 127. The threaded implant of claim 117, further comprising a second blocker located between said upper and lower members for holding at least a portion of the upper and lower members apart where said second expander is located.
 128. The threaded implant of claim 117, wherein said upper and lower members are configured to cooperate with one another so as to stop said upper and lower members from being moved apart from one another more than a predetermined distance.
 129. The threaded implant of claim 117, further comprising an expander located between said upper and lower members for moving at least a portion of the upper and lower members away from one another to increase the maximum height of said implant where said expander is located.
 130. The threaded implant of claim 129, wherein said expander rotates to increase the height of said implant.
 131. The threaded implant of claim 129, wherein said expander is located proximate an end of said implant opposite said blocker.
 132. The threaded implant of claim 129, wherein said implant has a longitudinal axis and said expander rotates in a plane perpendicular to the longitudinal axis of said implant to increase the height of said implant.
 133. The threaded implant of claim 131, wherein said hollow is substantially unobstructed by said expander extending along a substantial portion of the length of said hollow so as to permit growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 134. The threaded implant of claim 131, wherein said expander remains in the same location along the longitudinal axis of the implant when rotated.
 135. The threaded implant of claim 129, wherein each of said upper and lower members have a track within which said expander rotates.
 136. The threaded implant of claim 129, wherein said expander has a first height corresponding to the height of said expander when said implant is initially inserted into the spine, said expander having a second height corresponding to the height of said expander when said expander is moved into a final deployed position to increase the height of said implant, said second height being greater than said first height.
 137. The threaded implant of claim 117, wherein said upper and lower members have walls contacting one another.
 138. The threaded implant of claim 137, wherein said walls are aligned parallel with the longitudinal axis of said implant.
 139. The threaded implant of claim 137, wherein said walls are at least in part overlapping.
 140. The threaded implant of claim 117, wherein said upper and lower members have a rotational articulation therebetween adjacent one of said proximal end and said distal end of said upper and lower members.
 141. The threaded implant of claim 140, wherein said rotational articulation is at one of said proximal end and said distal end of said upper and lower members opposite said blocker.
 142. The threaded implant of claim 140, wherein said rotational articulation allows for expansion.
 143. The threaded implant of claim 142, wherein said rotational articulation allows for limited expansion.
 144. The threaded implant of claim 140, wherein said rotational articulation is formed by said upper and lower members interdigitating so as to cooperatively engage.
 145. The threaded implant of claim 144, wherein said rotational articulation is configured such that engagement occurs when said upper and lower members are substantially perpendicular to one another.
 146. The threaded implant of claim 145, wherein said rotational articulation is configured to remain engaged within a range of movement of said upper and lower members resulting from positioning said implant in the second position.
 147. The threaded implant of claim 117, wherein one of said upper and lower members has an interior wall, which is unexposed, extending therefrom toward the other of said upper and lower members when said implant is in an initial insertion position, and when said implant is in a final position said implant has a shape such that each of said arcuate portions of said upper and lower members are separated by at least a portion of said interior wall, which now has an exposed side.
 148. The threaded implant of claim 147, wherein said upper and lower members have side walls for engaging each other.
 149. The threaded implant of claim 148, wherein said side walls of said upper and lower members are at least partially overlapping walls.
 150. The threaded implant of claim 147, wherein said arcuate portions of said upper and lower members form an angular orientation relative to one another when said implant is in the final position.
 151. The threaded implant of claim 147, wherein said arcuate portions of said upper and lower members when said implant is in the initial insertion position form a cylindrical shape.
 152. The threaded implant of claim 117, wherein said implant has an interior, at least one of said upper and lower members has a screw hole passing therethrough adapted to receive a screw passing from said interior of said implant into one of the adjacent vertebral bodies.
 153. The threaded implant of claim 152, wherein each of said upper and lower members has at least one screw hole passing therethrough adapted to receive a screw passing from said interior of said implant into the adjacent vertebral body in contact with each of said upper and lower members respectively.
 154. The threaded implant of claim 152, further comprising at least one screw adapted to pass from said interior of said implant through said screw hole and into the adjacent vertebral body to anchor said implant to the adjacent vertebral body.
 155. The threaded implant of claim 117, wherein said implant has a side surface when in a final position that is contoured to cooperate with another implant.
 156. The threaded implant of claim 155, wherein said implant and said cooperating other implant have a combined width therebetween less than the combined height of said implant and said cooperating other implant.
 157. The threaded implant of claim 117, further comprising a cap for closing one of said proximal end and said distal end of said upper and lower members, said cap having an exterior surface and an interior surface.
 158. The threaded implant of claim 157, wherein said interior surface of said cap has spaced slots about its circumference to facilitate a snap fit of said cap into said implant.
 159. The threaded implant of claim 117, wherein said implant comprises an artificial material other than bone.
 160. The threaded implant of claim 117, wherein said implant is made of an artificial material that is stronger than bone.
 161. The threaded implant of claim 117, wherein said implant is made of an artificial material that is harder than bone.
 162. The threaded implant of claim 117, wherein said implant comprises bone.
 163. The threaded implant of claim 162, wherein said bone includes cortical bone.
 164. The threaded implant of claim 117, wherein said implant comprises bone growth promoting material.
 165. The threaded implant of claim 164, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.
 166. The threaded implant of claim 117, wherein said implant is treated with a bone growth promoting substance.
 167. The threaded implant of claim 117, wherein said implant is a source of osteogenesis.
 168. The threaded implant of claim 117, wherein said implant is at least in part bioabsorbable.
 169. The threaded implant of claim 117, wherein said implant comprises metal.
 170. The threaded implant of claim 169, wherein said metal is ASTM material suitable for use said threaded spinal fusion implant.
 171. The threaded implant of claim 169, wherein said metal includes titanium.
 172. The threaded implant of claim 117, wherein said implant comprises a plastic material.
 173. The threaded implant of claim 117, wherein said implant comprises a ceramic material.
 174. The threaded implant of claim 117, wherein said implant is formed of a porous material.
 175. The threaded implant of claim 117, wherein said implant is formed of a material that intrinsically participates in the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 176. The threaded implant of claim 117, wherein said implant has an interior surface and a hollow defined therein, said hollow being capable of containing bone growth promoting material.
 177. The threaded implant of claim 176, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.
 178. The threaded implant of claim 117, wherein said at least one opening is adapted to retain fusion-promoting materials
 179. The threaded implant of claim 117, wherein at least a portion of said implant is treated to promote bone ingrowth between said implant and said adjacent vertebral bodies.
 180. The threaded implant of claim 117, in combination with a chemical substance to inhibit scar formation.
 181. The threaded implant of claim 117, wherein said blocker is an expander having an external thread, each of said upper and lower members having a threaded converging portion adapted to cooperate with said external thread of said expander to expand said implant from a first collapsed height to a second expanded height when said expaner is rotated from a first to a second position.
 182. A threaded interbody spinal fusion implant for at least in part rotational insertion across a disc space between two adjacent vertebral bodies of a spine, said implant comprising: an upper member having a portion being at least in part arcuate adapted for placement toward and at least in part within one of the adjacent vertebral bodies, said upper member having at least one opening adapted to communicate with one of the adjacent vertebral bodies, said upper member having a proximal end and a distal end; a lower member having a portion being at least in part arcuate adapted for placement toward and at least in part within the other of the adjacent vertebral bodies, said lower member having at least one opening adapted to communicate with the other of the adjacent vertebral bodies, said openings of said upper and lower members being in communication with one another and adapted for permitting for the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant and being sufficiently sized and located to allow for interbody spinal fusion through said implant, said lower member having a proximal end and a distal end corresponding to said proximal end and said distal end of said upper member, respectively, and a length between said proximal and distal ends, said upper and lower members articulating therebetween adjacent one of said proximal ends and said distal ends of said upper and lower members and allowing for expansion of the height of said implant, said upper and lower members having a first position relative to one another allowing for a collapsed implant height and a second position relative to one another allowing for an increased height, said arcuate portions of said upper and lower members in the first position being parallel to one another over a substantial portion of the length of said implant and forming at least a portion of a cylinder along the length of said implant; at least a portion of a helical thread formed on the exterior of each of said opposed arcuate portions of said upper and lower members for penetrably engaging the adjacent vertebral bodies and to facilitate securing said implant into the spine by at least in part rotating said implant about the longitudinal axis of said implant; and at least one expander adapted to expand said upper and lower members from the first position to the second position when moved from an expander insertion position to a final deployed expander position, said expander being adapted to cooperatively engage and hold at least a portion of said upper and lower members apart so as to maintain the increased height of said implant and resist the collapse of said implant to the collapsed implant height when said implant is in a final deployed position, said expander having a first height corresponding to the height of said expander when said implant is initially inserted into the spine, said expander having a second height corresponding to the height of said expander when said expander is rotated into a final deployed position to increase the height of said implant, said second height of said expander being greater than said first height of said expander.
 183. The threaded implant of claim 182, further comprising a hollow defined between said upper and lower members in communication with said openings in each of said upper and lower members, said hollow being adapted to receive fusion-promoting substances, said hollow having a width that is substantially unobstructed by any mechanism for moving said expander.
 184. The threaded implant of claim 182, wherein said implant has a constant width in both the collapsed height and the increased height.
 185. The threaded implant of claim 182, wherein said implant has a width and said expander has a width less than the width of said implant.
 186. The threaded implant of claim 182, wherein said implant has a width and said expander has a width less than one half the width of said implant.
 187. The threaded implant of claim 182, wherein said implant has side walls and said expander does not contact said side walls when said implant is in the final deployed position.
 188. The threaded implant of claim 182, wherein said implant has a longitudinal axis and said expander rotates in a plane generally perpendicular to the longitudinal axis of said implant to increase the height of said implant.
 189. The threaded implant of claim 182, wherein said expander is located along the length of said implant.
 190. The threaded implant of claim 182, wherein said expander is located proximate said proximal ends of said upper and lower members.
 191. The threaded implant of claim 182, wherein said expander is located proximate said distal ends of said upper and lower members.
 192. The threaded implant of claim 182, wherein said expander remains in the same location along the longitudinal axis of the implant when rotated.
 193. The threaded implant of claim 182, wherein said expander is located at a predetermined location along the length of said implant and remains so located in transitioning said implant from the first position to the second position.
 194. The threaded implant of claim 182, wherein said expander is adapted to cooperatively engage a tool used to move said expander from an initial position to a final position to increase the height of said implant, said tool not being a part of said implant and being removed from said implant after moving said expander into the final position.
 195. The threaded implant of claim 182, wherein said expander is adapted to cooperatively engage a tool that rotates about an axis parallel to the longitudinal axis of said implant to rotate said expander to increase the height of said implant.
 196. The threaded implant of claim 195, wherein said expander rotates in a plane perpendicular to the longitudinal axis of said implant to increase the height of said implant.
 197. The threaded implant of claim 196, wherein said expander remains in the same location along the longitudinal axis of the implant when rotated.
 198. The threaded implant of claim 182, wherein said expander moves said arcuate portions of said upper and lower members from a parallel orientation to an angled orientation relative to one another.
 199. The threaded implant of claim 182, wherein each of said upper and lower members are adapted to cooperate with said expander.
 200. The threaded implant of claim 199, wherein each of said upper and lower members have a track configured to permit said expander to rotate therein.
 201. The threaded implant of claim 200, wherein said tracks permit said expander to move from side to side within said track.
 202. The threaded implant of claim 199, wherein said track of said upper member and said track of said lower member are in the same plane.
 203. The threaded implant of claim 199, wherein said track of said upper member and said track of said lower member are parallel to one another.
 204. The threaded implant of claim 199, where said track of said upper member and said track of said lower member are in a plane perpendicular to the longitudinal axis of said implant.
 205. The threaded implant of claim 182, wherein said upper and lower members structurally cooperate with said expander so as to keep said expander located within said implant.
 206. The threaded implant of claim 199, wherein at least one of said tracks of said upper and lower members has a cooperating surface, said expander having a corresponding cooperating surface that contacts said cooperating surface of said at least one track to orient said expander in a predetermined location.
 207. The threaded implant of claim 206, wherein said cooperating surfaces orient said expander within said implant such that the axis of rotation of said expander is parallel with the longitudinal axis of said implant.
 208. The threaded implant of claim 207, wherein said cooperating surfaces center said expander within said implant such that the axis of rotation of said expander coincides with the longitudinal axis of said implant.
 209. The threaded implant of claim 182, wherein said upper and lower members are configured to cooperate with one another so as to stop said upper and lower members from being moved apart from one another more than a predetermined distance.
 210. The threaded implant of claim 199, wherein said upper and lower portions are adapted to cooperate with said expander so as to center said expander within a cross section of the upper and lower portions.
 211. The threaded implant of claim 199, wherein at least one of said tracks of said upper and lower members includes at least one side having a cooperating surface, said expander having a corresponding cooperating surface that contacts said cooperating surface of said at least one side to orient said expander in a predetermined location.
 212. The threaded implant of claim 211, wherein said cooperating surface of said at least one side is a detent and said corresponding cooperating surface of said expander is a projection.
 213. The threaded implant of claim 212, wherein said detent and said projection center said expander within said implant such that the axis of rotation of said expander coincides with the longitudinal axis of said implant.
 214. The threaded implant of claim 182, wherein said expander has an upper surface, a lower surface, and side surfaces as defined when said expander is positioned to increase the height of said implant, said side surfaces intersecting said upper and said lower surfaces at two diametrically opposed junctions.
 215. The threaded implant of claim 214, wherein said two diametrically opposed junctions are a pair of diametrically opposed corners and a pair of diametrically opposed arcs.
 216. The threaded implant of claim 214, wherein each of said upper and lower surfaces lie generally in a plane.
 217. The threaded implant of claim 214, wherein said upper and lower surfaces are generally parallel to one another.
 218. The threaded implant of claim 214, wherein said side surfaces and said upper and lower surfaces are oriented to substantially form a parallelogram.
 219. The threaded implant of claim 182, wherein the difference between said first height and said second height of said expander approximates the difference in height of said implant between said first position and said second position as measured proximate the location of said expander.
 220. The threaded implant of claim 215, wherein said two diametrically opposed arcs are each of the same radius.
 221. The threaded implant of claim 220, wherein the distance across said two diametrically opposed arcs generally approximates the distance between said upper and lower surfaces of said expander.
 222. The threaded implant of claim 215, wherein said two diametrically opposed corners form a 90-degree angle.
 223. The threaded implant of claim 182, wherein said expander has a depth dimension less than that of said first and second height of said expander.
 224. The threaded implant of claim 223, wherein said expander has a fixed shape during movement from an initial insertion position to a final deployed position within said implant.
 225. The threaded implant of claim 182, further comprising a second expander located between said upper and lower members for moving at least a portion of the upper and lower members away from one another to increase the maximum height of said implant where said second expander is located.
 226. The threaded implant of claim 225, wherein said second expander rotates to increase the height of said implant.
 227. The threaded implant of claim 225, wherein said second expander is located proximate an end of said implant opposite said expander.
 228. The threaded implant of claim 225, wherein said implant has a longitudinal axis and said second expander rotates in a plane perpendicular to the longitudinal axis of said implant to increase the height of said implant.
 229. The threaded implant of claim 227, wherein said hollow is substantially unobstructed by said second expander extending along a substantial portion of the length of said hollow so as to permit growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 230. The threaded implant of claim 227, wherein said second expander remains in the same location along the longitudinal axis of the implant when rotated.
 231. The threaded implant of claim 225, wherein said second expander is located proximate one of the proximal end and the distal end of said upper and lower members.
 232. The threaded implant of claim 231, wherein said hollow is unobstructed by said second expander extending along a substantial portion of the length of said hollow to permit growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 233. The threaded implant of claim 231, further comprising a second hollow between said upper and lower member located between said second expander and said end of said implant proximate said second expander.
 234. The threaded implant of claim 225, wherein each of said upper and lower members have a track within which said second expander rotates.
 235. The threaded implant of claim 223, wherein said track is configured to permit said second expander to rotate therein and then to move from side to side within said track.
 236. The threaded implant of claim 225, wherein said second expander has a first height corresponding to the height of said second expander when said implant is initially inserted into the spine, said second expander having a second height corresponding to the height of said second expander when said second expander is moved into a final deployed position to increase the height of said implant, said second height being greater than said first height.
 237. The threaded implant of claim 225, wherein said second expander has an upper surface, a lower surface, and side surfaces as defined when said second expander is positioned to increase the height of said implant, and said side surfaces intersecting said upper and said lower surfaces at two diametrically opposed junctions.
 238. The threaded implant of claim 237, wherein the difference between said first height and said second height of said second expander approximates the difference in height of said implant between said first position and said second position as measured proximate the location of said second expander.
 239. The threaded implant of claim 182, wherein said upper and lower members have walls contacting one another.
 240. The threaded implant of claim 239, wherein said walls are aligned parallel with the longitudinal axis of said implant.
 241. The threaded implant of claim 239, wherein said walls are at least in part overlapping.
 242. The threaded implant of claim 182, wherein said upper and lower members have a rotational articulation therebetween adjacent one of said proximal end and said distal end of said upper and lower members.
 243. The threaded implant of claim 242, wherein said rotational articulation is at one of said proximal end and said distal end of said upper and lower members opposite said expander.
 244. The threaded implant of claim 242, wherein said rotational articulation allows for expansion.
 245. The threaded implant of claim 244, wherein said rotational articulation allows for limited expansion.
 246. The threaded implant of claim 242, wherein said rotational articulation is formed by said upper and lower members interdigitating so as to cooperatively engage.
 247. The threaded implant of claim 246, wherein said rotational articulation is configured such that engagement occurs when said upper and lower members are substantially perpendicular to one another.
 248. The threaded implant of claim 247, wherein said rotational articulation is configured to remain engaged within a range of movement of said upper and lower members resulting from positioning said implant in the second position.
 249. The threaded implant of claim 182, wherein one of said upper and lower members has an interior wall, which is unexposed, extending therefrom toward the other of said upper and lower members when said implant is in an initial insertion position, and when said implant is in a final position said implant has a shape such that each of said arcuate portions of said upper and lower members are separated by at least a portion of said interior wall, which now has an exposed side.
 250. The threaded implant of claim 249, wherein said upper and lower members have side walls for engaging each other.
 251. The threaded implant of claim 250, wherein said side walls of said upper and lower members are at least partially overlapping walls.
 252. The threaded implant of claim 249, wherein said arcuate portions of said upper and lower members form an angular orientation relative to one another when said implant is in the final position.
 253. The threaded implant of claim 249, wherein said arcuate portions of said upper and lower members when said implant is in the initial insertion position form a cylindrical shape.
 254. The threaded implant of claim 182, wherein said implant has an interior, at least one of said upper and lower members has a screw hole passing therethrough adapted to receive a screw passing from said interior of said implant into one of the adjacent vertebral bodies.
 255. The threaded implant of claim 254, wherein each of said upper and lower members has at least one screw hole passing therethrough adapted to receive a screw passing from said interior of said implant into the adjacent vertebral body in contact with each of said upper and lower members respectively.
 256. The threaded implant of claim 254, further comprising at least one screw adapted to pass from said interior of said implant through said screw hole and into the adjacent vertebral body to anchor said implant to the adjacent vertebral body.
 257. The threaded implant of claim 182, wherein said implant has a side surface when in a final position that is contoured to cooperate with another implant.
 258. The threaded implant of claim 257, wherein said implant and said cooperating other implant have a combined width therebetween less than the combined height of said implant and said cooperating other implant.
 259. The threaded implant of claim 182, further comprising a cap for closing one of said proximal end and said distal end of said upper and lower members, said cap having an exterior surface and an interior surface.
 260. The threaded implant of claim 259, wherein said interior surface of said cap has spaced slots about its circumference to facilitate a snap fit of said cap into said implant.
 261. The threaded implant of claim 182, wherein said implant comprises an artificial material other than bone.
 262. The threaded implant of claim 182, wherein said implant is made of an artificial material that is stronger than bone.
 263. The threaded implant of claim 182, wherein said implant is made of an artificial material that is harder than bone.
 264. The threaded implant of claim 182, wherein said implant comprises bone.
 265. The threaded implant of claim 264, wherein said bone includes cortical bone.
 266. The threaded implant of claim 182, wherein said implant comprises bone growth promoting material.
 267. The threaded implant of claim 266, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.
 268. The threaded implant of claim 182, wherein said implant is treated with a bone growth promoting substance.
 269. The threaded implant of claim 182, wherein said implant is a source of osteogenesis.
 270. The threaded implant of claim 182, wherein said implant is at least in part bioabsorbable.
 271. The threaded implant of claim 182, wherein said implant comprises metal.
 272. The threaded implant of claim 271, wherein said metal is ASTM material suitable for use said threaded spinal fusion implant.
 273. The threaded implant of claim 271, wherein said metal includes titanium.
 274. The threaded implant of claim 182, wherein said implant comprises a plastic material.
 275. The threaded implant of claim 182, wherein said implant comprises a ceramic material.
 276. The threaded implant of claim 182, wherein said implant is formed of a porous material.
 277. The threaded implant of claim 182, wherein said implant is formed of a material that intrinsically participates in the growth of bone from adjacent vertebral body to adjacent vertebral body through said implant.
 278. The threaded implant of claim 182, wherein said implant has an interior surface and a hollow defined therein, said hollow being capable of containing bone growth promoting material.
 279. The threaded implant of claim 278, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.
 280. The threaded implant of claim 182, wherein said at least one opening is adapted to retain fusion-promoting materials
 281. The threaded implant of claim 182, wherein at least a portion of said implant is treated to promote bone ingrowth between said implant and said adjacent vertebral bodies.
 282. The threaded implant of claim 182, in combination with a chemical substance to inhibit scar formation.
 283. The threaded implant of claim 182, wherein said blocker is an expander having an external thread, each of said upper and lower members having a threaded converging portion adapted to cooperate with said external thread of said expander to expand said implant from a first collapsed height to a second expanded height when said expaner is rotated from a first to a second position. 